What's at stake in a NC Senate debate? Plenty

CNBC's John Harwood breaks down the key Senate race taking place in North Carolina between Democratic Senator Kay Hagan and Republican state House Speaker Thom Tillis.

RALEIGH, N.C.—Every important element in the battle for control of the U.S. Senate comes into focus here in North Carolina.

The race features a Democratic incumbent, Kay Hagan, whose party is counting on her winning a second term to hold its majority. Just like five of her Democratic Senate colleagues.

It takes place in a state that Mitt Romney carried over Barack Obama two years ago. Just as in six other battleground races.

It features strong Republican attacks on a president with dwindling popularity—and strong Democratic counterattacks on a Republican Party with big image problems of its own. Just like in every other targeted race this year.

Bill Clark and Douglas Graham | CQ Roll Call | Getty Images

Sen. Kay Hagan and Thom Tillis

As a result, the debate Wednesday night between Hagan and her Republican opponent, Thom Tillis, will offer a window into the fall strategies of Democrats and Republicans alike this fall. The confrontation at the University of North Carolina's television studios at the Research Triangle Park gives Tillis an array of alternative attack lines, from Obamacare to various foreign policy crises. At the same time, Hagan faces choices on whether to focus attacks on economic issues or social and cultural themes, as well as controversy over the state's new law changing voting procedures, which the Obama Justice Department has challenged in court as discriminatory.

Hagan won her seat in 2008 amid an extraordinary surge by Democratic-leaning voters who made Obama the first Democrat to carry North Carolina for president in three decades. But North Carolina flipped back to Republicans for Romney two years ago. And the altered political environment here—the governorship also flipped from blue to red in 2012—poses a stiffer test with a smaller expected turnout from Democratic-friendly groups such as blacks, Latinos, young voters and single women.

The Democrat has some mobilizing tools available to her that stand out on the national landscape. While Democrats everywhere attack the tax and spending priorities of Republicans in Congress, Washington gridlock gives an abstract air to some of their barbs. But North Carolina has been a tea party-era case study in fulfilling those priorities through tax cuts and spending restraints, and Tillis stands at the center of it as speaker of the North Carolina House.

The agenda of the Republican-controlled General Assembly and newly installed Gov. Pat McCrory have sparked a series of liberal protests called Moral Mondays. Those lend fuel to Hagan's campaign in a state whose changing economy (through the increasing presence of a high-technology industry and its highly educated workers) and demography (a population gradually becoming more Latino and less rural) have given Democrats new opportunities to compete.

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Polls show an extremely tight race. And Wednesday night's debate at 7 p.m. EDT, televised nationally on C-SPAN, as well as within North Carolina, gives both candidates the chance to begin breaking it open.